The present invention relates to the actuation elements of a rotating dobby.
Rotating dobbies for forming the shed in weaving looms are known to be constituted by the assembly, side by side, along a principal shaft driven in an intermittent movement of rotation with a stop every 180.degree., of a series of actuation elements which are placed under the control of a programmed reading device and of which each is connected to one of the heddle frames mounted on the corresponding loom.
The invention relates more particularly to rotating dobbies of the type disclosed in French Patent No. 2 596 425 of Mar. 26, 1986 to STAUBLI. As schematically shown in FIG. 1 of the accompanying drawings, which Figure reproduces FIG. 1 of the Patent in question, the frame 1 supports the intermittently rotating principal shaft 2 which drives the actuation elements of the dobby. Each element includes a connecting rod 3 coupled to a lever 4 connected to one of the frames 5 of the loom. Each connecting rod 3 has an opening therein in which is engaged, with the interposition of a roller bearing 6, an eccentric 7 mounted idly on shaft 2 via a roller bearing 8. In addition, there is associated with each connecting rod 3 a driver plate 9 which is secured to the shaft 2, provided to be splined to that end, and which has two opposite notches 9a therein, adapted to cooperate with a coupling hook 10 mounted on a small pin 11 carried by a projecting plate secured to the eccentric 7.
Pivoting of the hook against its return spring 12 is controlled by two selector levers 13 which pivot at 14 and which are coupled to one another by a small rod 15. With one of these levers 13 are associated two pivoting rods 16 that needles 17, placed under the control of a programmed reading device 18, conduct to a position such that the rods are or are not placed opposite the reciprocating stroke of two pushers 19. There is associated with one of the levers 13 a spring 20 which tends to maintain the opposite lever in abutment against a fixed stop 21.
When the hook 10 is subjected to the action of its spring 12, the eccentric 7 is coupled to shaft 2, with the result that the connecting rod 3 is pivoted by an oscillating movement which displaces the frame 5 vertically. On the contrary, when this hook receives the action of one of the levers 13, its outer edge comes into contact with a resiliently urged bolt 22 carried by a small fixed pin 23, with the result that it is immobilized and that it in turn immobilizes the connecting rod 3 shown.
In principle, such an arrangement makes it possible to obtain reliable functioning even at high speeds of rotation, but this advantageous result is obtained only with a drastic monitoring of the different elements constituting the actuation elements, this, in addition, involving very meticulous assembly operations. It will be readily appreciated that even the slightest defect in the positioning of the pivot pins 11 (hook 10) and 23 (bolts 22) or in the profile of the notches made in the plates 9 and in the back of the hook mentioned, automatically makes correct functioning impossible.
It is a principal object of the present invention to overcome this drawback in conventional rotating dobbies.